The present invention relates to an eyeglass-frame-shape measuring device for measuring a lens frame shape such as a shape of a lens-fitting portion of an eyeglass frame, and an eyeglass-lens processing apparatus having the measuring device.
An eyeglass-frame-shape measuring device is disclosed, for instance, in U.S. Pat. No. 5,228,242. In the disclosed measuring device, a feeler is biased against the frame groove of a frame held by a frame holding section to be kept in contact with the frame groove, and the feeler thus kept in contact with the frame groove is moved along the frame groove. The measuring device obtains the information on movement of the feeler to measure the lens frame shape of the frame. The measuring device of this type uses an urging force of a spring to bias the feeler against the frame groove (i.e., in the direction of the radius vector of the frame shape (or the target lens shape)) in measurement.
However, the eyeglass-frame-shape measuring device suffers from the following problems.
(1) With the method of biasing the feeler using the spring, the spring expands and contracts depending on the radius vector of the frame, so that the urging or pressing force against the frame during measurement is not constant. To cope with frames of various shapes and eliminate the dislocation of the feeler from the frame groove during measurement, the force of a certain degree needs to be applied to the frame groove even in the state in which the spring is contracted (a portion whose length of the radius vector is long). If measurement is effected with the force of the spring thus determined, a large pressing force is applied to the frame groove in a portion whose length of the radius vector is short, which may causes deformation on a materially or structurally soft frame. To perform measurement without deforming the frame, it is desirable to apply such a pressing force as to be weak but not to cause the feeler to be dislocated, and to apply the pressing force to the frame groove constantly. PA0 (2) With the method of biasing the feeler using of the spring, it is necessary to substantially horizontally maintain the holding of the frame by a frame holding section and a feeler moving mechanism section without tilting them, and therefore the degree of freedom in the layout of the device is restricted. Namely, if the feeler moving mechanism section is tilted, the pressing force of the feeler varies depending on the angular direction of the radius vector in measurement due to the effect of its own weight, so that the possibility of the deformation of the frame and the dislocation of the feeler from the frame groove becomes large. PA0 (3) After the insertion of the feeler into the frame groove, the feeler is generally set in a free state so as to be movable vertically along the frame groove. Therefore, the feeler is likely to be dislocated in the case of a frame having large warp.